Special Instructions

Method Name

PBB: Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

ZPPB: Hematofluorometry

Reporting Name

Lead Profile Occ Exposure, B

Specimen Type

Whole blood

Specimen Required

Patient Preparation:

High concentrations of gadolinium and iodine are known to
interfere with most metals tests. If either gadolinium- or
iodine-containing contrast media has been administered, a specimen
should not be collected for 96 hours.

Supplies:

Metal Free B-D Tube (EDTA), 6 mL (T183)

Metal Free (Lead only) EDTA Tube, 3 mL (T615)

Microtainer (EDTA) Tube, 0.5 mL (T174)

If ordering the EDTA trace element Vacutainer tube from BD,
order catalog #368381

1. See Trace Metals Analysis Specimen Collection and Transport
in Special Instructions for complete instructions.

2. Send specimen in original tube.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type

Temperature

Time

Whole blood

Refrigerated

28 days

Reject Due To

Hemolysis

Mild reject; Gross reject

Lipemia

Mild reject; Gross reject

Icterus

NA

Other

Clotted specimen, Green top heparin tube

Clinical Information

Lead is a heavy metal commonly found in man's environment that
can be an acute and chronic toxin.

Lead was banned from household paints in 1978, but is still
found in paint produced for nondomestic use and in artistic
pigments. Ceramic products available from noncommercial suppliers
(such as local artists) often contain significant amounts of lead
that can be leached from the ceramic by weak acids such as vinegar
and fruit juices. Lead is found in dirt from areas adjacent to
homes painted with lead-based paints and highways where lead
accumulates from use of leaded gasoline. Use of leaded gasoline has
diminished significantly since the introduction of nonleaded
gasolines that have been required in personal automobiles since
1972. Lead is found in soil near abandoned industrial sites where
lead may have been used. Water transported through lead or
lead-soldered pipe will contain some lead with higher
concentrations found in water that is weakly acidic. Some foods
(for example: moonshine distilled in lead pipes) and some
traditional home medicines contain lead.

Lead expresses its toxicity by several mechanisms. It avidly
inhibits aminolevulinic acid dehydratase (ALA-D) and
ferrochelatase, 2 of the enzymes that catalyze synthesis of heme;
the end result is decreased hemoglobin synthesis resulting in
anemia.

Lead also is an electrophile that avidly forms covalent bonds
with the sulfhydryl group of cysteine in proteins. Thus, proteins
in all tissues exposed to lead will have lead bound to them. The
most common sites affected are epithelial cells of the
gastrointestinal tract and epithelial cells of the proximal tubule
of the kidney.

The typical diet in the United States contributes 1 to 3 mcg of
lead per day, of which 1% to 10% is absorbed; children may absorb
as much as 50% of the dietary intake, and the fraction of lead
absorbed is enhanced by nutritional deficiency. The majority of the
daily intake is excreted in the stool after direct passage through
the gastrointestinal tract. While a significant fraction of the
absorbed lead is rapidly incorporated into bone and erythrocytes,
lead ultimately distributes among all tissues, with lipid-dense
tissues such as the central nervous system being particularly
sensitive to organic forms of lead. All absorbed lead is ultimately
excreted in the bile or urine. Soft-tissue turnover of lead occurs
within approximately 120 days.

Avoidance of exposure to lead is the treatment of choice.
However, chelation therapy is available to treat severe disease.
Oral dimercaprol may be used in the outpatient setting except in
the most severe cases.

Erythrocyte protoporphyrin is a biologic marker of lead
toxicity. Lead inhibits several enzymes in the heme synthesis
pathway and causes increased levels of RBC zinc protoporphyrin
(ZPP).

Reference Values

LEAD

All ages: 0.0-4.9 mcg/dL

Critical values

Pediatrics (≤15 years): ≥20.0 mcg/dL

Adults (≥16 years): ≥70.0 mcg/dL

ZINC PROTOPORPHYRIN

<100 mcg/dL

All measurements assume hematocrit of 42% and are made in mcg/dL
per OSHA requirements.

Interpretation

The Centers for Disease Control and Prevention (CDC) has
identified the blood lead test as the preferred test for detecting
lead exposure in children. Chronic whole blood lead levels below 10
mcg/dL are often seen in children. For pediatric patients, there
may be an association with blood lead values of 5 to 9 mcg/dL and
adverse health effects. Follow-up testing in 3 to 6 months may be
warranted. Chelation therapy is indicated when whole blood lead
concentration is above 25 mcg/dL in children or above 45 mcg/dL in
adults.

The Occupational Safety and Health Administration (OSHA) has
published the following standards for employees working in
industry:

-Employees with whole blood lead levels above 60 mcg/dL must be
removed from workplace exposure.

-Employees with whole blood lead levels above 50 mcg/dL averaged
over 3 blood samplings must be removed from workplace exposure.

-An employee may not return to work in a lead exposure
environment until their whole blood lead level is below 40
mcg/dL.

-All measurements assume hematocrit of 42% and are made in
mcg/dL per OSHA requirements.

Elevated zinc protoporphyrin (ZPP) levels in adults may indicate
long-term (chronic) lead exposure or may be indicative of iron
deficiency anemia or anemia of chronic disease.

Clinical Reference

1. National Report on Human Exposure to Environmental
Chemicals. Centers for Disease Control and Prevention. Updated Feb
2015. Available at http://www.cdc.gov/exposurereport

2. Occupational Safety and Health Administration: OSHA Lead
Standard-Requirements from the General Industry Standards Lead
(1910, 1025), from 29 CFR 1910, 1025, A.M. Best Safety and
Security-2000. Retrieved July 2016. Available at
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10033